Ball wear mechanisms and control in the grinding of sulfide and phosphate ores

Marked ball grinding tests were carried out in the laboratory using high carbon low alloy steel (cast and forged) and high chrome cast iron balls. Relative ball wear as a function of grinding period and milling conditions was evaluated for the different type of ball materials in the grinding of lead-zinc sulphide and phosphate ores. Results indicated that ball wear increased with time and showed a sharp increase for wet grinding over dry grinding. Ball wear under wet grinding conditions was also influenced by the gaseous atmosphere in the mill. The influence of oxygen on the corrosive wear of grinding balls was increasingly felt in case of sulphide ore grinding. The grinding ball materials could be arranged in the following order with respect to their overall wear resistance:

Characterization of a variant glucose-6-phosphate dehydrogenase from the south Indian population.

Glucose-6-phosphate dehydrogenase (G6PD) is coded by a gene on the X-chromosome. Earlier studies have shown that the South Indian population has a high incidence of this enzyme deficiency. The electrophoretic mobility, pH optimum and the K-m values for G6PD from normal and variant individuals were identical. However, the specific activity of the variant enzyme was 8 times less compared to the value of the normal enzyme. Western blot analysis of partially purified G6PD from normal and variant individuals performed using equal amounts of total protein showed that the variant protein was 3 times less in concentration. Similar analysis performed using protein corresponding to equal enzyme activity units in the normal and variant samples showed that the variant enzyme was 2.25 times less efficient compared to the normal enzyme. RNA dot blot analysis using full length G6PD cDNA probe (PGDT5B, a kind gift from Prof. L Luzzatto) revealed that lymphocytes from normal and variant individuals had equal amounts of G6PD specific mRNA.

Effects of halogen substitution in nucleic acid components. Structure of sodium 5-bromocytidine 5'-phosphate hydrate

The conformation of 5-bromocytidine 5'-monophosphate in the title compound, Na+.C9H11BrN3O8P-.1.25H2O, is anti, C(3')-endo and gauche-gauche, similar to that in analogous non-halogenated nucleosides/nucleotides. The Na ion coordinates directly with phosphate O atoms and base atoms. Br is not involved in any stacking interaction.

A method for in vivo [32P]phosphate labelling of testis proteins

The direct intratesticular injection of [P-32]phosphate resulted in 4-9 times more labelling of rat testis proteins compared to the conventional method of in vitro incubation. Moreover this is a simple technique requiring minimum (7-10 times less) radioactive phosphate and is less hazardous.

Effect of phosphate adsorption on the permeability of clays

In this paper, the effect of phosphate anion adsorption on the permeability values of homoionized kaolinite and montmorillonite clays is presented. The homoionized sodium, calcium and hydrogen clays are prepared by repeatedly washing the clays with 2N solutions of corresponding chlorides. Phosphate adsorption was induced by treating homoionized clays with phosphoric acids for different periods varying upto 1000 hrs. The coefficient of permeability of the clays was determined from one dimensional consolidation test results. The decrease in the permeability of kaolinite clays on phosphate adsorption has been explained on the fabric changes. For montmorillonite, both cation exchange and phosphate adsorption causes significant changes which are explained based on variation in the thickness of diffuse double layer.

Insertion of nickel nanoparticles in the interlayers of alpha-zirconium phosphate by the decomposition of the intercalated nickel acetate

By employing EXAFS and magnetic measurements, it is shown that nanoparticles of nickel along with those of NiO are incorporated between the layers of a-zirconium phosphate (ZrP) by the thermal decomposition of nickel acetate intercalated in ZrP. The nickel nanoparticles are superparamagnetic. Hydrogen reduction produces small ferromagnetic nickel particles, most of which appear to be outside the interlayer space of ZrP.

Interaction of sheep liver apo-serine hydroxymethyltransferase with pyridoxal-5'-phosphate: A physicochemical, kinetic, and thermodynamic study

Sheep liver serine hydroxymethyltransferase (EC 2.1.2.1) is a homotetramer of M(r) 213,000 requiring pyridoxal-5'-phosphate (PLP) as cofactor, Removal of PLP from the holoenzyme converted the enzyme to the apo form which, in addition to being inactive, was devoid of the characteristic absorption spectrum. Upon the addition of PLP to the apoenzyme, complete activity was restored and the visible absorption spectrum with a maximum at 425 nm was regained. The interaction of PLP with the apoenzyme revealed two phases of reaction with pseudo-first-order rate constants of 20 +/- 5 s(-1) and 12.2 +/- 2.0 x 10(-3) s(-1), respectively. However, addition of PLP to the apoenzyme did not cause gross conformational changes as evidenced by circular dichroic and fluorescence spectroscopy. Although conformationally apoenzyme and holoenzyme were indistinguishable, they had distinct apparent melting temperatures of 51 +/- 2 and 58 +/- 2 degrees C, respectively, and the reconstituted holoenzyme was thermally as stable as the native holoenzyme. These results suggested that there was no apparent difference in the secondary structure of holoenzyme, apoenzyme, and reconstituted holoenzyme, However, sedimentation analysis of the apoenzyme revealed the presence of two peaks of S-20,S-w values of 8.7 +/- 0.5 and 5.7 +/- 0.3 S, respectively. A similar pattern was observed when the apoenzyme was chromatographed on a calibrated Sephadex G-150 column. The first peak corresponded to the tetrameric form (M(r) 200,000 +/- 15,000) while the second peak had a M(r) of 130,000 +/- 10,000. Reconstitution experiments revealed that only the tetrameric form of the apoenzyme could be converted into an active holoenzyme while the dimeric form could not be reconstituted into an active enzyme. These results demonstrate that PLP plays an important role in maintaining the structural integrity of the enzyme by preventing the dissociation of the enzyme into subunits, in addition to its function in catalysis. (C) 1996 Academic Press, Inc.

Phosphate derivatives of 123 cuprates of the formula LnSr(2)Cu(3)O(7) (Ln=Gd, Dy, Ho)

Partial substitution of Cu in the chain by the phosphate ion stabilizes LnSr(2)Cu(3)O(7) (Ln = Gd, Dy or Ho) in the 123 structure. The LnSr(2)Cu(2.8)(PO4)(0.2)O-y derivatives exhibit incommensurately modulated structures. The holmium oxy-phosphate derivative has been rendered superconducting by the partial substitution of Ho by Ca.

Solubilization of n-decane into n-decyl-polyoxyethylene surfactants: A cavity forming free energy based model

The present paper reports the results of a theoretical study of the forces and factors driving the solubilization of n-alkane solubilizates into the micellar core of some non-ionic surfactants, based on a micellar model which includes the cavity forming free energy as a component of micellization. The solubilizate is n-decane and the non-ionic surfactants considered are n-decyl-polyoxyethylene surfactants. The extent of solubilization, i.e. the mole fraction of the solubilizate within the core has been calculated. The results indicate that the incorporated solubilizate has more translational and rotational degrees of freedom as compared to those of the tail parts of the surfactants present in the core. This drives the total free energy of aggregation after solubilization into a more favourable direction. The results are in fair agreement with the experimental results.

Investigations on sodium tin phosphate and tin pyrophosphate glasses

Glasses of the alkali tin phosphate system have been investigated. The infrared absorption and fluorescence spectra of the glasses have been examined. It is found that tin is present in both + 2 and + 4 oxidation states. Also tin ions occupy four- or six-coordinated sites in the glass.

New open-framework phosphate and phosphite compounds of gallium

Five new open-framework compounds of gallium have been synthesized by hydrothermal methods and their structures determined by single crystal X-ray diffraction studies. The compounds, C8N4H26]Ga6F4(PO4)(6)], I, C5N3H11]Ga3F2(PO4)(3)]center dot H2O, II, C6N3H19]Ga-4(C2O4)(PO4)(4)(H2PO4)]center dot 2H(2)O, III, Ga2F3(HPO4)(PO4)]center dot 2H(3)O, IV, and C3N2H5](2)Ga-4(H2O)(3)(HPO3)(7)], V, possess three-dimensional structures. All the compounds are formed by the connectivity between the Ga polyhedra and phosphite/phosphate units. The observation of SBU-6 (I and II) and spiro-5 (IV) secondary building units (SBUs) are noteworthy. The flexibility of the formation of gallium phosphate frameworks has been established by the isolation of two related structures (I and II) from the same SBU units but different organic amines. Some of the present structures have close resemblance to the gallium phosphate phases known earlier. The compounds have been characterized by CHN analysis, powder XRD, IR, and TGA. (C) 2011 Elsevier B. V. All rights reserved.

Laboratory studies on the volume change characteristics of kaolinite contaminated with sodium phosphate/sulfate

Reported distress to an industrial structure from phosphate/sulfate contamination of kaolinitic foundation soil at an industrial location in Southern India prompted this laboratory study. The study examines the short-term effect of sodium sulfate/phosphate contamination on the swell/compression characteristics of a commercial kaolinite. Experimental results showed that the unsaturated contaminated kaolinite specimens exhibited slightly higher swell potentials and lower compressions than the unsaturated uncontaminated kaolinite specimens. It is suggested that the larger double layer promoted by the increased exchangeable sodium ion concentration is responsible for the slightly higher swell potentials and lower compressions of the unsaturated contaminated kaolinite specimens.

Polyethylene stibinite phosphate esters: Novel flame-retardant plasticizers for PVC

A new series of multielement flame-retardant plasticizers containing polyethylene stibinite phosphate esters have been prepared by bulk polymerization from ethylene glycol with various antimony (III) aryloxydichlorides and arylphosphorodichloridates possessing various combinations of substituent [Cl,Br,NO2]. All the polymers are pink-coloured viscous fluids. They were characterized by inherent viscosity, density, IR, H-1, C-13 and P-31 NMR spectroscopy. The thermal behaviour of the polymers was compared by thermogravimetric analysis and correlated with their structures. The flammability studies were carried out by the limiting oxygen index test. The polymers containing P, Sb, N and Pr elements in their backbone show superior thermal-and flame-retardant characteristics than the other polymers. A comparative study was carried out with one of the synthesized polymers as a polymeric flame-retardant additive to plasticized PVC. The results showed improved LOI and mechanical properties to that of the conventional flame-retardant additive composition. (C) 1997 Elsevier Science Ltd.